"We think that everything is in order, nobody is injured," he told The Associated Press.
No ransom demands have been made yet, the company said.
Lt. Nathan Christensen, a Bahrain-based spokesman for the U.S. 5th Fleet, said the ship was seized off the southern coast of Yemen, about 60 miles (95 kilometers) from the town of al-Mukalla, the capital of the Hadramaut region.
Robin Phillips, deputy director of the Bahamas maritime authority in London, said the Longchamp had been traveling in a corridor secured by EU military forces when it sent a distress signal before dawn.
"Ships and helicopters were dispatched, but they arrived too late," said Phillips, adding that gunshots could be heard over the radio. He said the ship later set a course for Somalia, to the south.
Liquefied petroleum gas is a mixture of gases used to fuel heating appliances and vehicles.
Piracy has taken an increasing toll on international shipping, especially in the Gulf of Aden, which links the Mediterranean Sea and the Suez Canal with the Indian Ocean. Pirates made an estimated $30 million hijacking ships for ransom last year, seizing more than 40 vessels off Somalia's 1,900-mile (3,000-kilometer) coastline.
Somali waters are now patrolled by more than a dozen warships from countries including Britain, France, Germany, Iran and the United States. China and South Korea have also ordered warships sent to the region to protect their vessels and crews from pirates.
The warships have helped many cargo ships fight off the pirates, but Christensen said they were not near the Longchamp when it was taken.
He also said 21 ships since Dec. 1 have taken "aggressive, evasive maneuvers" and successfully evaded pirate attacks.
The German military reported two more suspected attempts by pirates to attack ships in the Gulf of Aden early Thursday. A German navy frigate received an emergency call from a cargo ship, the European Champion, which reported that it was being followed by a skiff. A military statement said the skiff backed off after the German ship sent its on-board helicopter to the scene.
A second cargo ship, the Eleni G., radioed that it was being pestered by several skiffs. A German frigate sailed toward the ship, which shook off the suspected pirates.
Somalia, a nation of about 8 million people, has not had a functioning government since warlords overthrew a dictator in 1991 and then turned on each other. Its lawless coastline is a haven for pirates.
Cyrus Mody of the International Maritime Bureau said 166 crew on nine ships were still being held off the coast of Somalia, not including the Longchamp. Six other hijacked ships have been released this month, including an oil tanker freed for a reported $3 million ransom.
Noel Choong, who heads the International Maritime Bureau's piracy reporting center, said Thursday's hijacking was the first attack since Jan. 14. For the past two weeks, strong winds have made it difficult for pirates to launch their small boats, but the weather has now improved, Choong said.
There have been 15 attacks so far this year, and three ships seized, he said.